This invention relates to motor control systems, and in particular, to a data interface module which allows a user to modify a predetermined number of operating parameters of an AC induction motor from a remote location and for displaying such parameters.
There are two basic approaches for controlling the starting, stopping and speed of an AC induction motor. In a first approach, an adjustable frequency controller is interconnected to the AC induction motor. The adjustable frequency controller is comprised of an inverter which uses solid state switches to convert DC power to stepped waveform AC power. A waveform generator produces switching signals for the inverter under control of a microprocessor. While adjustable frequency controllers efficiently control the motor speed and the energy used by an AC induction motor, use of such types of controllers may be cost prohibitive. Further, since many applications of AC induction motors do not require sophisticated frequency and voltage control, an alternative to adjustable frequency controllers has been developed.
An alternate approach to the adjustable frequency controller is the soft starter. Soft starters operate using the principal of phase control whereby the three phase main supply to the AC induction motor is controlled by means of anti-parallel thyristor switches in each supply line. In phase control, the thyristor switches in each supply line are fired to control the fraction of the half cycle over which current is conducted to the motor, known as the conduction period. The non-conducting period of each half cycle (known as the hold-off angle or the notch width) is visible as a notch in the voltage waveform at each motor terminal. During this period, no current flows to the motor terminals. To end the non-conducting period, the thyristor switches in the supply line to the motor terminals are fired to restart their conduction. The conduction through the thyristor switches continues until the current, once again, becomes zero at some point in the next half cycle and the thyristor switches reopen. According to the principles of phase control, by varying the duration of the non-conducting period, the voltage and current supplied to the AC induction motor may be controlled. As is known, a single microprocessor has been used to fire the thyristor switches in order to control the voltage and current supplied to the AC induction motor.
In order to accurately control the starting, stopping and speed of the AC induction motor, the microprocessors used in adjustable frequency controllers and the soft starters must execute extensive control algorithms. High performance microprocessors are necessary to perform the numerous calculations required at an acceptable computational speed. The types of high performance microprocessors are expensive and increase the overall cost of the motor control. Therefore, it is highly desirable to provide a motor control system which provides the desired control of the motor at a lower cost.
In addition, use of a single microprocessor in motor control applications limits the flexibility of such motor control. Heretofore, motor controls have been built as single, integral units. Such units provide for limited input and output options for the user. As a result, prior art motor controls limit a user""s ability to monitor certain operating parameters or require special hardware to order to have certain operating parameters displayed or controlled. Therefore, it is highly desirable to provide a motor control which allows for greater flexibility for the users thereof
Therefore, it is a primary object and feature of the present invention to provide a motor control system which incorporates distributed processing to reduce the cost and improve performance of the motor control system.
It is a still further object and feature of the present invention to provide a motor control system which increases the flexibility for the users thereof.
It is a still further object and feature of the present invention to provide an input/output device for a motor control system which is simple to use and inexpensive to manufacture.
In accordance with the present invention, a data interface module is provided for allowing a user to modify predetermined operating parameters for a motor driven by a motor control and for displaying the operating parameters. The motor control is operatively connected to a communications network for transmitting and receiving data. The data interface module includes a visual display structure operatively connected to the communications network. The visual display structure selectively displays one of a plurality of user selected screens. The user selected screens include a first screen for displaying a user scrollable list of operating parameters for the motor and a second screen for displaying a data value for the user selected operating parameter. A screen selection device is operatively connected to the visual display structure for allowing a user to toggle between the first and second screens.
A micro-controller is operatively connected to the visual display structure and a communications link which, in turn, interconnects the micro-controller to the communications network. The communications link receives a predetermined packet of data from the motor control corresponding to the data value of the user selected operating parameter and provides the same to the micro-controller such that the micro-controller causes the visual display structure to display the data value of the user selected operating parameter on the second screen.
A data value adjustment device is operatively connected to the micro-controller for adjusting the data value of the user selected operating parameter displayed to a user selected data value. The data value adjustment device includes a shaft encoder wherein rotation of the shaft varies the data value of the user selected operating parameter of the motor.
A memory storage device may be operatively connected to the motor control for storing the user scrollable list of operating parameters. The memory storage device includes a serial EEPROM which is interfaced to the micro-controller by a serial peripheral interface. It is contemplated that the visual display structure include a liquid crystal display and that the screen selection device include a pushbutton movable between a first non-depressed position and a second depressed position wherein the pressing of the pushbutton into the depressed position toggles the visual display structure between the first and second screens. At least one of the screens of the visual display structure displays an operating direction for the motor. As such, it is contemplated to provide a motor direction scrolling device operatively connected to the visual display structure for changing the display of the operating direction of the motor. A motor direction selection device is also operatively connected to the motor controller for changing the operating direction of the motor to the operating direction displayed.
In accordance with a further aspect of the present invention, data interface module is provided for allowing a user to modify the value of predetermined operating parameters for a motor driven by a motor control and for displaying a value of the operating parameters. The motor control is operatively connected to a communications network. The data interface module includes a micro-controller for generating adjustment signals to adjust the value of a user selected operating parameter of the motor. A communications link interconnects the micro-controller and the communications network in order to transmit the adjustment signals to the motor control. A visual display structure is operatively connected to the motor controller. The visual display structure selectively displays one of a plurality of user selected screens. The user selected screens include a first screen for displaying a user scollable list of operating parameters for the motor and a second screen for displaying the value of the user selected operating parameter. A screen selection device is operatively connected to the visual display structure for allowing the user to toggle between the first and second screens. A parameter value adjustment device is operatively connected to the micro-controller and has a plurality of discrete settings. The micro-controller generates a corresponding adjustment signal in response to the setting of the parameter value adjustment device.
It is contemplated that the micro-controller include a universal asynchronous receiver/transmitter. The communications link includes a transceiver which is operatively connected to the universal asynchronous receiver/transmitter of the micro-controller and to the network.
It is contemplated that the micro-controller adjust the display of the value of the user selected operating parameter in response to the setting of the parameter value adjustment device. The parameter value adjustment device may include a shaft encoder wherein rotation of the shaft encoder varies the setting of the parameter value adjustment device.
At least one of the screens of the visual display structure displays an operating direction for a motor. Depression of a motor direction scrolling device causes the visual display structure to sequentially display each operating direction of the motor in response thereto. A motor direction selection device is provided for changing the operating direction of the motor to the operating direction displayed.
The micro-controller may include a plurality of micro-controller executable instructions stored thereon. Such instructions allow micro-controller to perform the steps of determining the types of motor controls interconnected to the communications network; downloading a list of predetermined operating parameters to be displayed on the first screen of the visual display structure from the motor control; and displaying a user selected portion of the list of the predetermined operating parameters on the first screen of the visual display structure.
In accordance with a still further aspect of the present invention, a method for allowing a user to modify the values of predetermined operating parameters for a motor driven by a motor control and for displaying the values of the operating parameters is provided. The method includes the steps of providing a data interface module having a visual display. The data interface module is interconnected to a communications network and determines the other motor controls also interconnected thereto. The data interface module downloads a list of predetermined operating parameters from the motor control and displays a user selected portion of the list of predetermined operating parameters on the visual display. A user selects one of the predetermined operating parameters to be displayed such that the data interface module displays the selected operating parameter and the value thereof on the visual display.
The method of the present invention may also include the additional step of adjusting the value of the selected operating parameter. In addition, the method may include the additional steps of displaying one of a plurality of operating directions of a motor on the visual display; scrolling through the plurality of operating directions of the motor on the visual display; and selecting one of the plurality of operating directions of the motor and providing the same as the selected motor direction. Thereafter, the motor is operated in the selected motor direction.
The data interface device may include a stop button such that depression of the stop button stops the motor. In addition, the data interface device may include a EEPROM which stores a list of predetermined operating parameters thereon.